Enzymes degrading enkephalin in bovine brain extracts have been resolved into two protein components needed to observe maximal activity for enkephalin degradation. The first component has been purified and identified as an aminopeptidase hydrolyzing the tyrosyl-glycine bond of enkephalin. This proposal involves a study of this aminopeptidase in terms of the substrate specificity. In addition an antibody to the enzyme will be prepared and used to study the localization of this enzyme and its rate of turnover under different physiological conditions. Specific inhibitors of the enzyme will be prepared and tested in vivo. The second component active in enkephalin degradation will be characterized in terms of its enzymatic activity and its relationship to the aminopeptidase will be assessed. Purification of this component and its characterization will be pursued in an attempt to elucidate a potential multi-component system involved in enkephalin degradation.